Significant research is being conducted to improve the efficiency and reduce the cost of energy generated by renewable resources. One such renewable energy resource is solar energy. Existing photovoltaic (PV) cells convert solar energy to electrical energy. Solar energy, or light, is composed of photons that strike the surface of the PV cell. However, a portion of the photons that reach the PV cell are reflected and still other photons are absorbed as heat. Only a portion of the photons that reach the PV cell: 1) reach the semiconductor material; and 2) transfer energy from the photon to the semiconductor material such that electrons in the semiconductor material are raised to a sufficiently high energy state that they are free to move within the semiconductor material, thereby generating electricity. Thus, a primary focus of research in PV cells is to improve the efficiency at which the PV cell converts the solar energy into electrical energy.
It is noted that the PV cells cannot directly store the electrical energy generated; therefore, the PV cell must be connected either to a load to immediately utilize the energy or to a storage device, such as rechargeable batteries, for subsequent usage. If the electrical energy is not used or transferred to a storage device, the excited electrons will recombine with the holes in the semiconductor material and the electrical energy is lost. Existing PV cells are, therefore, typically connected to rechargeable batteries such that energy generated but not immediately used by a load is stored for future use. However, the rechargeable batteries add additional cost and complexity in the system. Further, the batteries require extra space and have life cycle limitations. There are also concerns about recycling of old batteries. Thus, it would be desirable to provide a PV cell capable of storing the electrical energy directly in the PV cell without requiring the extra cost and complexity of an external storage device.
Therefore, it is a primary object and feature of the present invention to provide a photovoltaic capacitive device capable of directly harvesting and storing solar energy.
It is a further object and feature of the present invention to improve efficiency and reduce costs of photovoltaic systems by storing electrical energy within the PV cell rather than requiring external storage devices.
In accordance with the present invention, a device is provided for converting solar energy to electrical energy. The device includes a transparent electrode and a second electrode disposed opposite from the transparent electrode. A medium, which includes a semiconductor layer and a membrane layer, is disposed between the transparent electrode and the second electrode. The semiconductor layer may include a dipolar aprotic solvent, ferroelectric particles dissolved in the dipolar aprotic solvent, and semiconductor particles mixed in the solution of ferroelectric particles and dipolar aprotic solvent. The membrane layer may include an anhydrous aprotic solvent, ferroelectric particles dissolved in the anhydrous aprotic solvent, and an electrolyte mixed in the solution of ferroelectric particles and anhydrous aprotic solvent.
In accordance with other aspects of the invention, the transparent electrode may be glass sputtered with conductive indium tin oxide. The second electrode may be glass sputtered with gold. The semiconductor particles may be intrinsic silicon. The electrolyte may include a solution of ethylene carbonate and dimethyl carbonate with lithium hexafluorophosphate dissolved therein. The ferroelectric particles in each of the semiconductor layer and the membrane layer may be polyvinylidene fluoride. The dipolar aprotic solvent of the semiconductor layer may be N-methylpyrrolidinone. The anhydrous aprotic solvent of the membrane layer may be tetrahydrofuran.
In accordance with a further aspect of the present invention, a photovoltaic device for converting solar energy to electrical energy includes a transparent electrode, a second electrode disposed opposite from the transparent electrode, and a medium disposed between the transparent electrode and the second electrode further. The medium includes an electrolyte, semiconductor particles, ferroelectric particles bound with the semiconductor particles, and a membrane disposed on a surface of the second electrode.
In accordance with still another aspect of the present invention, a method is disclosed for storing electron hole pairs generated from light energy in a device. The device has a transparent electrode, a second electrode disposed opposite from the transparent electrode, and a medium disposed between the transparent electrode and the second electrode. The method includes the steps of receiving incident light at the medium through the transparent electrode and generating electron-hole pairs in the medium. The holes are injected into the transparent electrode, and the electrons are stored in the medium such that a voltage potential is established between the transparent electrode and the second electrode. The voltage difference is maintained when the incident light is removed.
In accordance with still yet aspect of the present invention, a method is provided for harvesting and storing solar energy in a device having a transparent electrode, a second electrode disposed opposite from the transparent electrode, and a medium disposed between the transparent electrode and the second electrode. The method includes the steps of generating electron-hole pairs via the photovoltaic effect responsive to solar energy being absorbed within the medium and establishing an ionic concentration gradient in the medium responsive to the electron-hole pair generation. The ionic concentration is maintained within the medium via the ferroelectric effect.
These and other objects, advantages, and features of the invention will become apparent to those skilled in the art from the detailed description and the accompanying drawings. It should be understood, however, that the detailed description and accompanying drawings, while indicating preferred embodiments of the present invention, are given by way of illustration and not of limitation. Many changes and modifications may be made within the scope of the present invention without departing from the spirit thereof, and the invention includes all such modifications.